Seal for assembling fluid-circuit tubular elements

ABSTRACT

The invention relates to an annular seal used for the telescopic mounting of a male end (10) of a first tubular element ( 1 ) in a socket ( 20 ) of a second tubular element ( 2 ). Said seal comprises an elastically-deformable annular body ( 3 ) designed to be threaded around the outer surface of the male end (10) and an anchoring lug ( 4 ) that only extends over part of the length of the body projecting radially around the latter and designed to be housed in an anchoring groove ( 25 ) disposed in the inner surface of the socket. At least one part of the lug ( 4 ) is made from a reinforcing material having a hardness greater than that of the body ( 3 ). Said seal is characterised in that the reinforcing material is located radially at a distance from the inner surface ( 32 ) of the body ( 3 ). Use: water supply and disposal networks.

The present invention concerns a seal for sealing, in a fluid circuit, atelescopic mounting between respective end regions in a mutual socketingrelationship of a first and a second tubular element, the end region ofthe first element called “male end” having an outer surface that isapproximately smooth, and that of the second element called “socket”having an inner surface provided with an anchoring groove, the sealbeing designed to be inserted and radially compressed between the outersurface of the male end and the inner surface of the socket.

Such an annular seal can be implemented to seal the joint between therespective fitted ends of two pipes, or of one pipe and a couplingsleeve, for example of cast iron, steel, or synthetic material, andparticularly to seal the mounting of pipeline elements of ductile castiron used in the construction of potable water supply or waste waternetworks.

In order to remedy the disadvantages of seals having a body designed tobe inserted and radially compressed between the fitted end regions oftwo tubular elements, and a rigid collar or a stiffening ring outsidethe socket intended to be supported against the front face of saidsocket to prevent the seal from being dragged to the bottom of thesocket when the male end is inserted thereinto, and more particularly totheir lack of reliability due to the vulnerability of the collar or ringto frontal impacts, seals have been designed comprising a collar or aring that are also intended to be inserted between the fitted endregions of the two elements and to that end constructed in the form ofan anchoring lug extending along part of the length of the body,projecting around the outer surface thereof, designed to be inserted inan anchoring groove made in the inner surface of the socket.

Since all of the seal must be inserted between the two elements, it mustbe relatively flexible, but this flexibility results in significantrisks that the lug may escape from the groove and the seal be draggedtoward to bottom of the socket when the male end is inserted into saidsocket, or it may be expelled out of said socket when the mounting isplaced under pressure.

Known, for example, is a seal having an elastically deformable annularbody designed to be threaded around the approximately smooth outersurface of the male end and an anchoring lug extending along part of thelength of the body, projecting around the outer surface thereof, thebody and the lug being made of a single piece of elastomer material witha Shore hardness of about 67°. In spite of this hardness, which requiressignificant effort to fit the male end into the socket, it is necessaryto provide in the inner surface of the socket an appreciably radial stopto hold the seal in the event it is dragged toward the bottom of thesocket when the male end is inserted into the socket. This stop istherefore positioned in front of the anchoring groove in the directiongoing toward the bottom of the socket, but naturally behind the free endof the male end in insertion position.

Also known, by the document DE GM 1 860 424, is a seal having a body andan anchoring lug, having a “rear” part (if reference is made to thedirection of fitting the male end into the socket) made of hard rubberto hold the seal in place during the fitting, and a “front” part offlexible rubber the compression of which is intended to ensure the sealof the mounting. However, here again the socket is provided with aninternal stop to hold the seal; moreover, the fitting first needs tocompress the hard rubber part, thus requiring significant fittingefforts.

Also known, by the document U.S. Pat. No. 2,953,398, is a composite sealof elastomer, reinforced at a rear part of its periphery (with the sameconvention of direction as mentioned above) to give it sufficientrigidity to prevent its being dragged along axially and having channelsor internal recesses to improve its flexibility during the fitting.Although this seal is made rigid, particularly in its anchoring part, itis not guaranteed to be held in place and the socket once again isfurnished with an internal stop to prevent its being pushed back towardthe bottom of the socket when the male end is inserted. In addition, themounting is still difficult because of the reinforcement of the seal ona large part of its periphery, and more particularly because of itsinner surface coming into sealing contact with the male end.

Moreover, the document FR 2 512 917 concerns a radial compression sealof a mono-hardness material provided with parallelepiped cells withsquare cross sectional shape. Although the cells give the seal greaterflexibility, allowing the mounting effort to be reduced, this solutionis still not sufficient because, since the seal is not rigidified, itrequires the use of a relatively hard elastomer to provide theanchoring, and the hardness of the elastomer increases the effortrequired for the mounting.

A purpose of the invention is to remedy these disadvantages, and to thatend concerns an annular seal intended to be inserted and radiallycompressed between the outer surface of a male end of a first tubularelement and the inner surface of the socket of a second tubular element,this seal having an elastically deformable annular seal body designed tobe threaded around the outer surface of the male end and an anchoringlug designed to be housed in an anchoring groove disposed in the innersurface of the socket, the body being delimited by two axial endsurfaces connected by an outer surface and by an inner seal surface andthe anchoring lug only extending over a part of the length of the body,projecting radially around the outer surface of said body, and at leastall of the free outer surface of the lug being made of a reinforcingmaterial having a hardness greater than that of the body, which seal ischaracterized in that the reinforcing material is situated radially awayfrom the inner surface of the seal body.

Because of this characteristic, the reinforcing material has no contactwith the male end whose outer surface, during the mounting, comes intocontact only with the inner surface of the seal body, said body beingmade of an easily compressible flexible material, the mounting effort isthus significantly limited.

In addition, because the anchoring lug is rigidified by a reinforcingmaterial of a hardness greater than that of the flexible body, the sealis then effectively anchored in the socket without the need to providean additional stop surface inside the inner surface of the socket. Thelug is therefore effectively held in the anchoring groove of the socketin both axial directions, that is, during the insertion of the male end,when the dragging of the seal toward the bottom of the socket isprevented, as well as when it is placed under pressure, when theexpulsion of the seal out of the socket, from the effect of forcestending to separate the tubular elements, is prevented.

Moreover, the seal can have one or more of the followingcharacteristics:

the anchoring lug extends axially exclusively between the two axialouter surfaces of the body, these two outer surfaces being freesurfaces;

the entire lug is made of a reinforcing material having a hardnessgreater than that of the body;

the lug has a part forming a core, made of the same material as the bodyand a reinforcing part that is made of a material having a hardnessgreater than that of the body and which constitutes an envelope-formingpart for the lug;

the envelope-forming part has vanes;

the vanes extend radially into the core forming part;

the vanes are tilted inside the core;

the reinforcing material having a hardness greater than that of the bodyalso has a melting point greater than that of the body;

the body is made of an elastomer material or elastomeric polymer;

the body is made of a material having a hardness within the range of 40°Shore to 60° Shore;

the reinforcing material, having a hardness greater than that of thebody, is a synthetic material;

the synthetic material is a thermoplastic material;

the thermoplastic material is a polyamide;

the body has cells;

the cells are in the shape of a truncated pyramid;

the truncated pyramids have a rhomboidal cross section;

one part of the outer surface of the body is a sealing surface;

the body, when it is not subject to exterior stress, has an outersurface of generally cylindrical shape;

the body, when it is not subject to stress, has a conical inner surface;

the body, when it is not subject to stress, has at least one outerconical surface;

the body has at least an outer surface into which the hollow cells inthe body open out; and

the lug has a longitudinal cross section generally trapezoidal in shape.

Other characteristics and advantages of the invention will becomeapparent from the following description, the forms of embodiment of theinvention being given by way of non-limiting examples and illustrated bythe attached drawings in which:

FIG. 1 is a diagrammatical longitudinal cross section of a part of aseal according to the invention in a first form of embodiment,

FIG. 2 is a diagrammatical longitudinal cross section of a part of atelescopic mounting of two pipe elements sealed by the seal of FIG. 1,

FIG. 3 is a partial front view of the seal of FIG. 1,

FIG. 4 is a partial front view showing details of the seal of FIG. 1,

FIG. 5 is a diagrammatical longitudinal cross section of a part of aseal according to the invention in a second form of embodiment, and

FIG. 6 is a partial cross section of the seal of FIG. 5 along the lineVI-VI of that figure.

The annular seals illustrated by the figures are intended to seal, in afluid circuit, a telescopic mounting of respective end regions of twotubular elements fitted to each other; these tubular elements, forexample, can be cylindrical pipes for waste water, one of which pipeshas an end forming a male end and the other has an end in the form of asocket forming a female end or socket, and although this is notrequired, this is the example that will be chosen for the presentdescription in order to simplify it.

Thus the first pipe 1 has an end forming a male end 10 which is intendedto be fitted into an end region of the second pipe 2 forming a socket20. In the selected example, respective longitudinal channels ofapproximately the same diameter run through the pipes 1, 2.

The male end 10 of the first pipe 1, intended to be mounted in thesocket 20 of the second pipe 2, has an outer surface of generallycylindrical shape 11 with circular cross section which is approximatelysmooth, provided at its free end with a beveled section 12.

The socket 20 into which the male end 10 is intended to be mounted hasan inner surface the bottom of which has an appreciably radial retainingcollar 21 intended to serve as stop for the free end of the male end,and going toward the free end of the socket, a first conical section 22flaring toward this free end and with taper approximately equal to thatof the beveled section 12, a section conical section 23 also flaringtoward this end but of slightly less taper, a cylindrical section 24,and a succession of sections (conical, cylindrical, conical), forming agroove 25 extending from the cylindrical section 24 toward the outerperipheral wall of the socket 20 as well as toward its free end withoutreaching it; the groove 25 ends at a nearly radial retaining collar 26from which there extend, going toward the free end of the socket 20, acylindrical section 27 and a conical section 28 flaring toward this freeend; the conical section of the groove 25, which extends from thecylindrical section 24, has a very large taper and constitutes aretaining collar, while the opposite conical section, which ends in theretaining collar 26, is sloped approximately 40 degrees.

The diameters of the second conical section 23 and the cylindricalsection 24 are markedly larger than that of the outer surface 11 of themale end 10 so as to constitute a chamber for the insertion of the seal,while the diameter of the cylindrical section 27 is only just larger soas to prevent the ejection of the seal when the mounting is placed underfluid pressure.

The annular seal illustrated by FIGS. 1 to 4 and of which FIG. 1 showsdiagrammatically a portion in longitudinal cross section, in the absenceof any exterior stress has an annular seal body 3 that is elasticallydeformable, designed to be threaded around the outer surface of the maleend 10, and an annular anchoring lug 4 extending only along a part ofthe length of the body 3, projecting radially around the outer surfaceof said body.

More specifically, the annular body 3 has an outer surface 31 thegeneral shape of which is approximately cylindrical, one part of whichprovides the seal with the inner surface of the socket 20 and thediameter of which is appreciably equal to that of the cylindricalsection 24 of the inner surface of the socket, and a conical innersurface 32 sloped at an angle a of about 20 degrees with reference tothe direction in which the outer surface extends, this inner surface 32of the body 3 also constituting the inner surface of the seal; the outersurface and the inner surface are connected by conical annular surfacesof axial end 33, 34 sharply sloped in the same direction, with respectto the outer surface 31; the direction of slope of these end surfaces33, 34 is such that in longitudinal cross section, the angles of one 33of the end surfaces respectively with the outer surface 31 and with theinner surface 32 are two acute angles while the angles of the other endsurface 34 respectively with the outer surface 31 and with the innersurface 32 are two obtuse angles, the first of these obtuse angles,however, being broken by a chamfer 35; by way of example, the angle β ofthe end surface 33 defining acute angles, with the perpendicular plan tothe outer surface, is about 10 degrees; the outer surface 31 has,approximately at mid-length, an annular groove 36 having a rounded walltoward the obtuse angles, and toward the acute angles a conical wallsloped at an angle y of about 27 degrees with reference to the outersurface.

The annular anchoring lug 4 is joined to the body 3 between the groove36 and the chamfer 35, in an area of the body 3 that is slightlyconcave. The lug 4 is therefore located completely away from the innersealing surface 32 and extends in outer radial projection around theouter surface 31 of the body 3; axially, the lug 4 extends between thetwo axial end surfaces 33, 34 of the flexible body 3, these end surfacesbeing free surfaces, that is, surfaces not covered by another material.As a result of the presence of the anchoring lug 4, the body 3 can becomprised of an elastically deformable material such as an elastomer ora relatively flexible elastomeric polymer with a hardness between 40°and 60° Shore (preferably around 50° Shore). In order to increase theflexibility of the body, it is possible to produce it so that it hascells 37 opening out into the annular end surface 33; these cells can bedistributed in this end surface around the circumference extendingapproximately at equal distance from the outer surface 31 and from theinner surface 32; each cell 37 here has the shape of a truncated pyramidwith an approximately rhombus shaped transverse cross section the largediagonal of which extends radially with reference to the body 3, whilethe edges of the truncated pyramid corresponding to this diagonal areapproximately parallel to the generatrices respectively of the outersurface 31 and of the inner surface 32 and converge toward to outersurface 34 having a chamfer 35. Preferably, the diagonals of the rhombusof the transverse cross section of the cells are such that the largeradial diagonal constituting the height of the rhombus is more thandouble the small diagonal constituting its width, which makes itpossible to uniformly distribute the radial compression of the body 3over the whole periphery and thus to achieve a uniform tightening andseal of the body 3 on the male end 10, and more particularly to theright of the radial diagonals of the rhombuses; the tops of the rhombusare slightly rounded so as not to generate a sharp truncated pyramidedge that could tear the body; the acute angle θ formed by the sides ofthe rhombus is around 45 degrees (FIGS. 3 and 4).

The annular anchoring lug 4 has a longitudinal cross section that isgenerally trapezoidal in shape the large base 41 of which, slightlyconvex, is united to the body 3 by the concave area of said bodyextending between the groove 36 and the chamfer 35, and the small base42 is approximately parallel to the generatrices of the outer surface 31so that the outer surface of the lug 4 is approximately cylindrical. Thesloped sides of the trapezoid are one slightly convex side 43 havingapproximately the same slope as the conical section of the groove 25 ofthe socket 20 extending from the side of the cylindrical section 24 ofsaid socket, and one side 44 located beside the chamfer 35 and sloped atan angle δ of about 40° with reference to the perpendicular plane at theouter surface 31 of the body 3. The full ring comprising the anchoringlug 4 is made of a synthetic reinforcing materials, for example athermoplastic such as a polyamide, adhered to the flexible materialscomprising the body 3, having a melting point greater than that of thisflexible material. The ring, however, should be flexible enough to allowthe deformation of the seal (and thus its own deformation) when the sealis installed in the socket. This ring can have one or more notches (notshown) to improve its deformability.

To manufacture the seal, the ring intended to form the lug 4 is placedat the bottom of a mold the shape of which corresponds to the desiredshape of the seal, then the elastomer is injected in the mold. Since themelting point of the material comprising the ring is greater than thatof the elastomer, the ring does not melt during the injection molding ofthe body and adheres to the elastomer.

As a variation (FIGS. 5 and 6), the annular anchoring lug 4 hasapproximately the same external aspect as that of FIGS. 1 to 4 but iscomposed of two parts, that is, a core 4A of a single piece with thebody 3 and made of the same material, thus of elastomer, and an envelope4B made of the same materials as the lug 4 of the form of embodiment ofFIGS. 1 to 4. Preferably the envelope 4B has vanes 45 extending into theelastomer of the core 4A, so as to confer on the lug the rigidity neededto hold it in the groove 25 of the socket while still preserving enoughflexibility to allow a suitable deformation of the seal when it isplaced in the chamber defined between the male end 10 and the socket 20,these vanes extending radially, for example, or sloped (FIG. IS 6) withreference to the radial direction to facilitate the compression of thelug when the groove 25 has a volume that is too confined. Because thelug has the same outer shape as in FIGS. 1 to 4, the envelope 4B has, inaddition to the vanes 45, a cylindrical wall corresponding to the smallbase 42 of the trapezoid, extending between two conical wallscorresponding to the sloped sides 43, 44.

Naturally, the forms described above are those, unless otherwiseindicated, of a seal that is not subject to any external stress.

To assemble the mounting, the seal is inserted into the socket 20, inthe absence of the male end 10, through the free end of the socket, andto do this the seal is deformed so as to be able to insert the lug 4into the groove 25 of the socket 20. Then the male end 10 is insertedinto the assembly, using force to deform the body 3 of the seal so thatits inner surface 32 takes a cylindrical shape coaxial to its outersurface 31, and it pressed against the outer surface 11 of the male end10 while the outer surface 31 of the seal is pressed against thecylindrical section 24 of the inner surface of the socket, which ensuresthe seal between the pipes 1, 2.

The rigidification of just the anchoring lug by a synthetic materialaway from the inner surface of the seal, and thus from the outer surfaceof the male end, makes it possible to limit the mounting effort andensures that the lug is held in place in its anchoring groove of thesocket. Moreover, the fact that the whole free outer surface of theanchoring lug is made of a reinforcing material prevents the seal frombeing dragged toward the bottom of the socket when the male end isinserted, as well as preventing the ejection of the seal out of thesocket from the action of the pressure of the fluid circulating in thepipes.

Furthermore, because of the effectiveness of the anchoring provided bythe composite seal according to the invention, it is possible toeliminate the stop at the bottom of the socket, thus making it possibleto shorten the socket and accomplish a gain in material, cast iron inthis instance, of the pipes.

The cells 37 disposed in the body 3 give the seal increased flexibilityand decrease still more the effort required for mounting.

Comparative tests between a seal such as the one shown in FIG. 1 and aseal of the same geometry made entirely of elastomer confirm that thecombination of an anchoring lug made of synthetic material (allowing theuse, for the seal body, of an elastomer or a flexible elastomericpolymer) with a body honeycombed with cells considerably reduces theeffort required for mounting, particularly when there is very littleclearance between the male end 10 and the socket 20, which makes itpossible to use a male end the free end of which is only slightlybeveled or even without any bevel.

In addition:

the cells promote the autoclave effect of the seal under the action ofthe internal pressure of the fluid circulating in the piping system,because the seal then performs much like a lip joint: the greater thefluid pressure that penetrates into the cells, the greater the pressureof the elastomer against the outer surface of the male end, thusensuring excellent performance at high internal pressures (more than 50bars); moreover, because of the autoclave effect, the seal fulfills itssealing function even when the internal pressure is low, unlike anon-hollowed compression body seal of the same type subjected to anidentical rate of compression and used for identical clearance betweenthe mounted tubular elements;

the pyramid shape of the cells makes it possible to have less elastomerto compress in the compression part of the body near the bottom of thesocket, compared to the parallelepiped cells, which contributes todecreasing even more the effort needed for mounting;

the cells improve the moldability of the seal, because the time of thecooling time of the elastomer during the molding process are reducedbecause of the smaller volume of elastomer to cool, which makes itpossible to reduce manufacturing costs;

the cells facilitate the factory pre-lubrication of the inner conicalsurface of the seal coming in contact with the male end during mounting,by means of a material with strong lubricating power and low coefficientof friction compatible with the elastomer, such as silicone grease orpolytetrafluoroethylene for sanitation piping, deposited as a film in athickness of a few micrometers.

as a result of the cells, the specific pressure at the lubricating filmis reduced during the mounting of the male end, which prevents the filmform being scraped away; in the absence of cells, it would be necessaryfor an operator to crease the seal and the male end on the constructionsite, in the trench (which is awkward and dangerous for the operator),using grease from a conventional can, with all the difficulties thatinvolves, particularly because of dirt being incorporated in the film ofgrease.

1. Annular seal intended to be inserted and radially compressed betweenthe outer surface of a male end (10) of a first tubular element (1) andthe inner surface of the socket (20) of a second tubular element (2),this seal having an elastically deformable annular seal body (3)designed to be threaded around the outer surface of the male end (10)and an anchoring lug (4) designed to be housed in an anchoring groove(25) disposed in the inner surface of the socket (20), the body (3)being delimited by two axial end surfaces (33, 34) connected by an outersurface (31) and by an inner seal surface (32) and the anchoring lug (4)only extending over a part of the length of the body (3), projectingradially around the outer surface (31) of said body, and at least all ofthe free outer surface of the lug (4) being made of a reinforcingmaterial having a hardness greater than that of the body (3), which sealis characterized in that the reinforcing material is situated radiallyaway from the inner surface (32) of the seal body (3).
 2. Seal accordingto claim 1, characterized in that the anchoring lug (4) extends axiallyexclusively between the two axial end surfaces (33, 34) of the body (3),these two end surfaces (33, 34) being free surfaces.
 3. Seal accordingto claim 1 or 2, characterized in that all of the lug (4) is made of areinforcing material having a hardness greater than that of the body(3).
 4. Seal according to claim 1 or 2, characterized in that the lug(4) has one part (4A) forming a core, made of the same material as thebody (3), and one part (4B) of reinforcement made of a material having ahardness greater than that of the body (3), and which constitutes anenvelope-forming part for the lug.
 5. Seal according to claim 4,characterized in that the envelope-forming part (4B) has vanes (45). 6.Seal according to claim 5, characterized in that the vanes (45) extendradially into the core-forming part (4A).
 7. Seal according to claim 5,characterized in that the vanes (45) are tilted inside the core (4A). 8.Seal according to any of claims 1 to 7, characterized in that thereinforcing material having a hardness greater than that of the body (3)also has a melting point greater than that of the body.
 9. Sealaccording to any of claims 1 to 8, characterized in that the body (3) ismade of an elastomer material or elastomeric polymer.
 10. Seal accordingto any of claims 1 to 9, characterized in that the body (3) is made of amaterial having a hardness within the range of 40° Shore to 60° Shore.11. Seal according to any of claims 1 to 10, characterized in that thereinforcing material, having a hardness greater than that of the body,is a synthetic material.
 12. Seal according to claim 11, the syntheticmaterial is a thermoplastic material.
 13. Seal according to claim 12,characterized in that the thermoplastic material is a polyamide. 14.Seal according to any of claims 1 to 13, characterized in that the body(3) has cells (37).
 15. Seal according to claim 14, characterized inthat the cells are in the shape of a truncated pyramid.
 16. Sealaccording to claim 15, characterized in that the truncated pyramids havea rhomboidal cross section.
 17. Seal according to any of claims 1 to 16,characterized in that one part of the outer surface (31) of the body (3)is a sealing surface.
 18. Seal according to any of claims 1 to 17,characterized in that the body (3), when it is not subject to exteriorstress, has an outer surface (31) of generally cylindrical shape. 19.Seal according to any of claims 1 to 18, characterized in that the body(3), when it is not subject to stress, has a conical inner surface (32).20. Seal according to any of claims 1 to 19, characterized in that thebody (3), when it is not subject to stress, has at least one outerconical surface (33, 34).
 21. Seal according to claim 20, characterizedin that the body (3) has at least an outer surface (33) into which thehollow cells (37) in the body open out.
 22. Seal according to any ofclaims 1 to 21, characterized in that the lug (4) has a longitudinalcross section generally trapezoidal in shape.